What fuel pressure range should I be seeing for a Lycoming IO-360 in a Lancair 360 (N360DE)?

 

The fuel pressure is indicating between 16 and 18 without the boost pump on.  When I go to altitudes above 6,000 feet, the fuel pressure drops a pound or two so I turn on the boost pump.  With the boost pump on fuel pressure in indicated between 18 and 20 PSI.

 

What is interesting is that the VM 1000 (where Fuel Pressure is indicated) has a red arc section, a yellow arc section, and a green arc section.  At the fuel pressures I am seeing; 16 PSI is in the top end of the yellow arc, so 17 to 20 PSI appears in the lower range of the green arc – giving us the feeling that we are on the ragged edge of not having proper fuel pressure for normal operation.

 

The VM-1000 can be calibrated so that the proper fuel pressure indicates more properly in the green arc – if this is proper.

 

Information that may be important to know:

 

IO-360 Model = Started life as O-360-C2A and converted to an IO-360 – S/N L-21393-36A

 

Fuel pressure is taken after the mechanical pump, 1 foot before the fuel servo on a tee fitting.

 

Fuel system/model/etc. = Bendix, model RSA 5AD1, parts list 2524213-10 less issues -11, S/N 9354/10

 

Have any components (fuel pump, servo, flow-divider, nozzles, etc.) been modified?  = Fuel servo mod: there was a mod made to the servo fuel injector to reverse the actuation of the butterfly valve and the fuel-metering valve.  When the throttle arm was rotated full forward; this was the idle position of the butterfly valve and the fuel-metering valve.  We had this reversed so that full forward position resulted in full throttle.

No other mods.

 

What type mechanical (engine-driven) fuel pump (diaphragm or rotary)? = Diaphragm

 

Thanks in advance.

 

Randy Hartman